Those are cumulus clouds, elevation 7,000 feet.
5 seconds sound clip from the White Christmas (1954) movie soundboard.
You can hear this line at 01:08:12 in the Blu-ray version of the movie.
Quote context
[...]
- Look, Bob, I still don't know too much about show business and guinea pigs...
- His inn-keeping days are numbered.
- Those are cumulus clouds, elevation 7,000 feet.
- Yeah, well, I wouldn't be surprised if it snowed overnight.
- I want to tell you something I haven't even told the womenfolk.
- Really?
- I've applied for active duty.
- Well, that's wonderful news, sir.
- I got an idea they may try to palm off one of those desk jobs on me, but they'd better not.
[...]